This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Objective: To determine noninvasively the effects of aging and reduced caloric intake on the physiological measures of sensitivity to sound stimuli. Caloric restriction (CR) is the only known method for increasing lifespan of laboratory animals. This study was conducted in conjunction with our larger investigation of CR in rhesus monkeys and it focused on the effects of CR and aging on measures of middle ear function measured with tympanometry. The intriguing significant findings demonstrating significant effects of age that differed by sex have been accepted for publication in the International Journal of Audiology in the near future. Longitudinal studies of the effects of age, sex, and diet as the animals age are continuing. This research used WNPRC Animal Services and Aging Resources.